Offset preventing in printing



"March s, 1938. 1 v. G. GREEN ET AL' 2,110,218

OFFSET PREVENTING IN PRINTING Original Filed Nov. 27, 1935 2 Sheets-Sheet l QQZL WM' March 8, 1938. v. s. GREEN ET AL OFFSET PREVENTING IN PRINTING Original Filed Nov. 27, 1935 2 Sheets-Sheet 2 (it :2 M

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OFFSET PREVENTING IN Virgil G. Green and Eric Gustafsson, Chicago, 111., assignors to Binks Manuiactnring Company, Chicago, lit, a corporation of Delaware Application November 27, 1935, Serial No. 51,742 V Renewed 1"ebruary2, 1938 22 Claims. (CL 101-420) 1.

Our invention relates to a method for avoid ing the production of offset (or smudge) by the piling of sheets upon one another after their imprinting, both foreiiminating the need of hav-' 5 ing socalled slip sheets temporarily inserted betweenthe consecutive sheets and for permitting a rapidly successive imprinting of another color on the same sheet.

For such offset-preventing it is alreadycusto- 0 maryon cylinderprinting presses to applya liquid ink-repellent or ink-drying material to the fresh- 1y imprinted sheet'by spraying such material (either downward or upward, aaccording to the direction in which the freshly made imprint on-the 5 sheet faces) upon the sheet, so as to coat or at least stipple the entire imprint with the inkrepellent.

This may bedon'e by having the freshly imprinted sheet pass under either'a single wide- :0 angled spray or under a row of sprays while that sheet is being conveyed to the delivery table on whichthe sheets are to be stacked; or the spraycoating (or spray-filming) of each sheet may be done after that sheet is already on the stack.

:5 In practice, this already customary procedure of spray-coating the freshly imprinted face of a sheet with'an offset-eliminating liquidhas the following objections:

' '(a) Since no single spray device can project a :0 spray of uniform density over an imprint of considerable area, a spraying of an adequate amount of offset-preventing material on some parts of the'imprint (as for example on those near the,

side edges of the sheet conveyer) can only be .5 obtained by also depositing a highly excessive amount of-material on other portions of the imprint. Consequently, the consumption hence cost) of this material is all out of propor tion tothe quantity which should be adequate,

n and the excess of such deposited material often interferes with the clarity of a later imprint of delaying the" successive imprinting of the same 5 sheet with another color.

(and

(d) The highly excessive quantity of offsetpreventing material also produces 9, correspond ingly increased amount of fumes, thereby requiring extensive fume exhaust provisions such as might not be needed in the same establishment if only theoperatively required amount of such material were sprayed, and also permitting the excessive fumes to damage parts of the printing press. 7

Our present method aims to overcome all of the above recited objections, and is based largely on the following observations:

e (1) When a modern spray gun, with a given adjustment, is so far from a surface toward which the gun is pointed that the spray no longer impacts against that surface, the spray becomes more highly atomized, and with relatively light sprayable materials, such as are suitable for 0H- set-prevention, the resulting misty spray becomes so diffused as to descend only slowly by gravity.

.. The process is capable of using any of the well known substances heretofore used for pre: venting offsetting in printing, such as those referredto and described in the United States Pate ent No. 2,007,404, granted July 9, 1935 ,toJohn MacLaurin, in the United States Patent No. 2,078,790, granted .April 27, 1937 on an applicationiiled December 24, 1931 by Edmond H. Bucy, in the British Patent #439,078, grantedto Jens A. Paasche and accepted November 28, 1935, and lame French Patent #784,826 granted to Jens A, Paasche, delivered May 6, 1935. e

(2) When such a spray is emittedonly momentarily and along an inclined axis, thepuif of spray forms a'misty cloud which is spread out somewhat horizontally during its descent.

(3) With a modern spray gun, air continues to issue from the gun for ashort time after the discharge of material from the gun has ceased. Consequently, if spray were projected only momentarily in a puffforming a temporarily floating cloud, this later issuing air additionally atomizes and spreads the cloud and also moves the cloud farther away from the gun.

(4) Whensuch a momentary puff of atomized material is projected toward the upper face of a sheet at a velocity which is insuflicient for havingthe resulting misty cloud impact against the sheet, theair below this cloud will slowly spread the cloud of mist to a larger horizontal area.

(5) When a freshly imprinted sheet is being dropped 'flatwise on a previously imprinted one,

the edge portions of the descending sheet curl up and the dropped sheet consumes. an appreciable time in flattening down on the previous one, presumably because the freshly dropped sheet has cloud before. the cloud' has gradually descended" to compress and gradually squeeze out the air between it and the sheet (6) If a cloud'of mist has been formed freely above a previously stacked sheet, as recited in-the next to the last preceding-paragraph, and ,a

freshly imprinted sheet is dropped above that on" the previously stacked sheet the squeezing out of the air between the two sheets during the descent of the freshly imprinted one flattens the cloud and spreads the cloud out horizontallyfto,

a greatly increased horizontal area. Consequently, a cloud of initially jmuch smallerhori-Z .zontal area than the imprinted face portioniof a' sheet.below it may have the material particles" of that cloud distributed printed face. 7

over this entire im- (7) 'Since the air thus squeezed out between the dropping sheet and the stationary one below itisof enormously greater volumethanthe air emitted. from the spray: device for projecting, the pull! or spray, the sprayed oiIset-preventing liquid is much more finely atomized. than. when sprayed directly" one stationary sheet, thereby making a 'I relatively quite small quantity. of such Imaterial madeimprintQ sem sters; causingthe freshly dropped sheet,- to,be .supported temporarily byjthe spaced particles of this material while the residual air between thetwo sheets aids in drying the. last Illustrative of the manner in which we :utilize the above observations,-v .J

Fig. 1 is a fragmentary rear endelevation of a" 'cylindebtype printing press provided with an at:-

' ta'chlnent forjspraying'pufis of ofisetipreventing material in timed. relationto theoperation of the presslwith'dotted lines f showing the path of the projected spray and the .initial'outline ofthe;

resulting cloud-of the sprayedmaterial.

Fig. 2' is a fragmentary side elevation of the same press, taken from the right-hand side of F E-' l 18- 3. Isa plan view bf {the'delivery table of v the same press'and of the spraying attachment,

with dotted linesshowing the emitted spray and theinitial Qutline' or the resulting cloud. Fig. 4 is a reducedrear end .viewof the delivery;

table of the press when this hash: numberof 4 sheets already stacked on it,'i andfshowing the next imprinted sheet in'the vposition.ifrorn which that she'etfis' dropped, and including adottedjout line showing the maximum initially advisable height of the cloud 'of 'ofiset-preventing.fmaterial below the said freshly imprintedisheet.

Fig. 5 is a viewsimila'r, tofFig. 4,".but taken after the dropping sheet has descended part way I toward jthestackpf sheets belowit, showingthe,

horizontal spreading-of the said cloud;

Fig. 6 is'a view allied to Fig.-',4,"showing'"the projecting of a suitable cloud ofofl'set preventing, material by. a spraydevice positioned forproject-. ing a sprayhori'zontaliy.- I j Fig. 7 is a fragmentary, side elevation of the rear end of a cylinder press in whicheach freshly imprinted sheet is dropp d from the arms of a Pivqtd e -d v chan sm 1' In the drawings, Figs. 1' to 3 show portions. of a conventional printing press in'which each 'f sheet. after it leaves the cylinder C slides down aninclined'guide 1, is then slid rearwardsgby a Y traveling sheetfeeder! propelled by a rocker arm 31 of the press, and inQWhich this. sheet is v re-, leased (by the, usually provided 1 means) whenit,

} previously piled on the delivery table. i

- 2,11 8 I is directly above the stack S of previously imprinted sheets on the delivery table T of the press. c

Fastened to one side of the rearward part of the press, as by brackets B attachedto a rear leg L of the'press, is a riser R, the upper end of which supports a material container 4. from which material can flow by gravity to a spray device 5 to which ahose .A also supplies compressed air.' This spraydevice preferably is supported from the riser R by a bracketi which can be adjusted as to its position both longitudinallyand rotationally of the said riser, and the spray device also preferably is pivoted to the said I bracket (as on a horizontal shaft 1) so that the user can readily vary the direction in which the spray (shown indotted lines at 8) is emitted.

,.To operate the spray device, we connect it to commercial solenoid types are well known) .to which circuit wires W lead from a switch III which has an arm Ilia adapted to jbe engagedby therocker arm 3,(or by atrip arm in. fastened :to

an electric. actuating device 9 (of which many the latter).-when the rocker armis momentarily near its most forward position. Manysuch solenoid actuated spraydevice have long been known, asattested fo.- example by the Burdick British Patent. #4211 of 1905 and by the Gradolph and Mueller (U. 8.), Patent #1,616,823.

, When the spray device isadjusted for emitting a sprayfv'v ith a velocity insuflicient for impacting the spray upon the sheet stacks, the spray I spreads asits velocity diminishes; and when this spray has been emitted as a mere pufl, the results ing mist forms a cloud, which (with the spray device constructed for iafine atomization) is so j light as to descend only quite-slowly by gravity..

Owing to this lightness, the cloud cannotreadily force the air below. it out of its way, so that the resistance of this air to compressioncauses the cloud to spread in horizontal area to forina cloud of. mist M. p I

With a proper adjustment of the spray device, which can readily bemadeafter a few trials. this cloudwill be disposed somewhat below the position" (shown in Fig. 4) from which the next 1 freshly imprinted sheet F is. dropped. after that sheet has'been moved rearward by the sheet feeder'2. During the descent of this sheet by gravity (in whatthe printers call airdroppingfi the squeezingoutof airbetween that sheet and the sheetstack 8- below it forces additional air upwards into the cloud,so. as to spread this firstto the larger horizontal area M! of Fig. 5 and to still larger area as the dropping .sheet approaches the said stack'moreand more, Moreover, withan unusually large imprint'area,fthe spray may be flattened byfhaving air emitted also from the usual horns 5:; (Fig. :1). of the spray device to.

spread the mist more widely before the dropping sheet strikes it.

With the switch thus. disposed so thatit' will be actuated onlypduringia small fraction of-the initial part of the rearward movement-of the arm3 which propels thesheet-sliding traveler 2, the'resultipg pufl of spray, although emitted at a velocity inadequate for propelling the spray all theway towardthe sheet stacks, has ample time for spreading intoa cloud disposed below the elevation fl-from which the'next sheet will be dropp d; Consequently, a quite simple mecha- Jnisnrsufiices forour purposes V 7 'Moreover, we have found in practice-that with our here presented method the quantity of ink repellent (or other offset-preventing) liquid needed for a given imprint is only a quite small percentage of what would be required by the previously customary practice of directly spraying the material against a sheetas for example, only about three percent. Owing to this small material consumption, a correspondingly small material container 4 suffices for a day's run of a press, so that we avoid the heretofore customary need of having an enormously larger material receptacle on an adjacent part of the floor (where it often is in the way of the press operator) and also eliminates the need of mechanical means for forcing the material from such a receptacle to the spray device.

Consequently, we can readily employ a gravity feed from the container 4 through a hose H to the spray device, and our entire installation can readily be detached from a given printing press by merely detaching the wires W fromthe switch on that press and loosening the clamps B This permits the same equipment to be transferred speedily to another press when the latter is provided with similar brackets B and also has a suitably disposed switch l0.

Owing to the extensive diminution of the required amount of offset-preventing material, we also correspondingly reduce the quantity of fumes produced by any such material, so that in a well ventilated printing establishment little or no fume-exhaust provisions will be needed. Furthermore, by directing the projected spray somewhat rearwardly with respect to the printing press, we eliminate the risk of having the offsetpreventing material gum or damage any operative part of the press.

Moreover, if the imprint is on the side of the sheet which faces downwards during the dropping of the sheet, the spray device can readily be adjusted in'position so as to dispose the cloud of material somewhat lower, if desired. Thus, Fig. 7 shows portions of a printing press in which the sheet is received from the cylinder C by delivery arms I! which swing the freshly imprinted sheet over the previously' stacked ones with the imprint facing downward.

So also, our method can be employed without any downward directing of the projected spray, so long as this is directed for producing a misty cloud of the material above the last previously stacked sheet and in the path through which the next imprinted sheet drops upon the stack. Thus, Fig. 6 shows such a cloud M as produced by a spray device a which flattens the projected spray along a horizontal plane and projects'this spray along a horizontal axis across which each airdropped sheet will move during its descent.

In practice, the forcing of air through a mist hovering above the imprint on an already stacked sheet expedites the evaporation of the liquid content of the particles of the mist, so that with the apparatus suitably adjusted, each such mist particle precipitates its solid content on the sheet in a nearly dry form. Consequently, if the material in the sprayed solution was a dextrin or other common constituent for adhesives, each such deposited particle will instantly adhere to the sheet and will then be further dried by the air which moves over it during the completion of the decent of the next sheet. However, offset is likewise prevented even on the top of the last stacked sheet because the mist gradually descends and upon that sheet, so that our method is not limited for use on sheets upon which others are thereafter to be stacked.

We claim as our invention:

1. A method of preventing offsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the steps of momentarily pulling an atomized spray of oflset preventing material to form a misty cloud above the last stacked sheet, and dropping the next sheet against said cloud to spread it and cause a distribution of the particles of the cloud over the surface of the last stacked sheet.

2. A method of preventing offsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the steps of momentarily projecting a spray of offset preventing material part way toward the last stacked sheet to form a misty cloud above said last stacked sheet, and dropping the next sheet against said cloud to spread it and cause a distribution of the particles of the cloud over the surface of the last stacked sheet.

3. A method of preventing oflsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the steps of momentarily projecting a spray of oflset preventing material part way toward the last stacked sheet to form a misty cloud of less horizontal spread than the imprinted portion of the last stacked sheet and above said last stacked sheet, and dropping the next sheet against said cloud to spread it and cause a distribution of the particles of the cloud over the surface of the last stacked sheet.

4. A method of preventing offsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the steps of creating a cloud of finely atomized offset preventing material of less horizontal spread than the imprinted portion of the last stacked sheet and above the last stacked sheet and in the path through which the next sheet is dropped, and dropping the next sheet against said cloud to squeeze it and the air between the last' stacked sheet and the next sheet during the descent of the latter whereby the material particles of the cloud are distributed over a larger horizontal area than said cloud initially had and whereby the particles will contact the opposed faces of the said two sheets.

5. A method of preventing offsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the steps of momentarily puffing an atomized spray of offset preventing material to form a misty cloud above the last stacked sheet and below the drop-starting position of the next sheet prior to the feeding of said next sheet to said position where the cloud will momentarily hover above the last stacked sheet, and dropping the next imprinted sheet against said cloud whereby the forcing out of the air between the last stack sheet and the next sheet will increase the atomization of the cloud and spread the particles of material over a larger horizontal area than that of the cloud.

6. A method of preventing offsetting in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the ,steps of momentarily projecting a finely atomized spray of liquid offset preventing material toward the last stacked sheet prior to the approach of the next sheet to form a cloud which momentarily hovers over said last stacked sheet and in the path of the next sheet, and dropping the next sheet against said cloud for forcibly moving the ,air through said cloud to spread the cloud particles further apart and to evaporate the liquid content of the particles.

:7 TL A method of preventing offset in printing wherein imprinted sheets are consecutively dropped to form a stack, comprising the stepsof momentarily projecting a finely atomized sprint of offset preventing material toward: the last stacked sheet to form armisty cloud initiallyhoveringvabove said last stacked sheet and in the path. through which theanextimprinted sheet f is;

I toqbe droppedandwith'anareal extent'less than over the surface of u thelast momentarily projecting a finely atomized spray of offset 1 preventing material toward the last Ming wherein imprinted sheets are consecutively" dropped to form a stack, comprising the steps of momentarily'pr'ojecting the finely atomized spray oI-offset preventing material toward the last] stacked sheet to form a'misty' cloud of less'area stacked sheet at a velocit'y'insuificient' for impacting the sheet'fbut sufiicientfor propelling the. spray particles into the path-through which thenext imprinted sheet drops to'form a cloud ,:above the: last 'stacked'sheet, and droppin'gthe next sheet againsts'aid cloud to"- spread it and cause a distribution of the particles of the cloud over the" surface of'the' last stacked sheet" I 9; A method ofpreventing oifse'ttingin print-,

than said sheet, timingfsaid spray 'projection' 'to finely divided create saidcloud before-the next imprinted sheet, reaches the position from which it ls 'dropped, and dropping the i next sheet 'againstvsaid'. cloud to spread it and cause a distribution'of the pai -fticles-of the cloud over the surface oftheflast stackedsheet I 10. A method'of preventing offsetting in print- 3 ing, comprising the steps of creating a cloud of I finely: divided particles from ofi'set preventing; material at a'locussp'aced from the surface of a" previously printed-sheet, and flattening said cloud by so dropping a successively printed sheet upon said cloud as to causeit' and the particles thereof I:

to spread at leastoverthe whole area of "the imprinted surfaceportionof theprinted sheet I 11. A method of preventing offsetting in print:

ing, comprising the steps of creating a cloucl of particles; .from offset preventing material at a locus above the surface of a pr'eviously printed sheet'and with a lesser areal ex tent than the area of the imprinted portion of said sheet, and so'moving a-successlvely' printed sheet through said locus toward 'said previously printed sheet as to increasethe'area of said cloud" and to causetheparticles to spread at'least over the entirearea .of the imprinted'surface portion of the printed sheet. 12. A method of preventing offsetting in' printting-comprising the steps of-so'sprayi'ng anofiset' "preventing material in liquid condition as to provide 'acloud offinely divided solidfo'rming particles at a-locus above the surface' of a previously printed sheet and with apredetermined areal ex tent relative to the area) of the imprinted portion i locus above the surface of a previously printed of the sheet, and so moving a successively printed sheet through said locus and against said cloudlf as to cause it and the particles thereof to spread at least over the entire-area of the imprinted surface portion of the printed sheet. I

13. A method of preventing offsetting in print-' ing, comprising the steps of so spraying an offset arrears particlesto spread at least. over the entire area of the imprinted surface portion of the printed sheet. 14. In a method of printing and delivering printedsheets, comprising the steps of delivering printedsheets in succession ingiven timeintervals,"creating a cloud of finely dividedfparticles from ofiset preventing material in each intervalbetween the delivering'of sheets, in the path thereof and at a locus above the surface 1 of the delivered previously printed sheet and with a given areal; extent less than the area of the successively delivered printed sheet to so pass through said-locus towar'd'said previously printed sheet as'to spread said cloud to cause the par: ticles thereof toat least cover the entire area of the imprinted surface'portion or saidfprinted sheets. I I

15. A method of preventing offset in printing during the delivery cfconsecutively imprinted sheets, comprising the momentary pufling of a finely atomized spray of offset preventingmate rial with 'a'ir' in a'direction towardthe imprinted 7 surface of a deliveredsheet and with insufiicient force to cause' fan. impact of the particles upon said, surface'so' 'as to eifect a'cloud "of finely divided; particlesat a locus spaced from said surface, and projecting sufficient air after the imprintedportlon of sai'd sheet," and causing'the discharge of said sprayas to cause a spreading of said cloud., I I e I -1 6. A method of preventing offset in printing whichcomprisesthejstepsioi' creating a cloud of extent than; said sheet, and then squeezing said cloud between said sh'eetand the next printed offset preventing material toward the last stacked sheet to i'orm a ;cl o'ud' 'abovei saidesheet of less areal, extent' than the area, of i the imprinted portion of said sheet and in the'path of move- I ment or the ne 'rtfsheet, and so moving said next sheet against said cloud as 'to squeeze said c1oud out to cover the whole area of said imprinted portion of the last stacked sheet.

fine particles from oifset preventing material op- 'posite a face of a printedsheet and offlss areal 18. A method of-preventing ofi'setting in' printproduce a'cloud'of finely divided particles at a sheet. and with; an areal extent less than the area in the spreading and the drying of the particles ing comprising the steps of spraying an offset preventing material in a fluid condition for a given interval of time, projectin a jet of air therewith: for a greater interval'of time and including thespray. interval of time soas to thereof, and so moving a successively printed sheet through said locus as to cause a lateral extension of said cloud and to cause the particles thereof to spread at least over the entire area of the imprinted surface portion of the printed sheet.

19. The method of preventing offset between imprinted sheets which are consecutively airdropped upon one another from a predetermined drop position to form a stack, which comprises the step of producing a fine misty cloud of a solution containing a solid forming constituent adapted to form spacer particles on the uppermost stacked sheet, in such a manner that the cloud floats above the last named sheet and at least mainly below the saidposition; and the step of thereafter dropping the next sheet from said position so that the squeezing out of air between said sheet during the descent thereof will spread the cloud horizontally and cause the evaporation of solvent from the particles con- 7 of said stacked sheet; and dropping the next suitable for sheet-spacing particles, into a misty cloud spaced upwardly from and opposite only a substantially central portion of a freshly imprinted stacked sheet, and so moving the next printed sheet through the locus of said cloud and toward the aforesaid sheet as to spread the cloud at least over the entire imprinted area portion of the first mentioned sheet.

22. The method of preventing printing offset by the depositing, upon a horizontal freshly imprinted sheet, of particles of the solid forming constituent of a solution thereof, which comprises the projecting of a spray of a quantity of such solution toward the upper face of the said sheet into the form of a cloud spaced from said sheet; and causing forcibly moved air to elongate the paths along which the spray particles move to the sheet, and to enhance the evaporation of solvent from the said particles during their travel through the said elongated paths, so as to effect a substantial drying of the said particles by the time they reach the sheet.

VIRGIL G. GREEN. ERIC GUSTAFSSON. 

